Abstract: The infrared target simulator is composed of infrared target image transmitter and the optical projection system. The infrared coupling optical system is a middleinfrared system with a long focal length, larger field and telecentric beam path in image space, which is required to match with the parameters of two homing optical systems. The optical design of infrared coupling system applied to infrared target simulator is presented in this paper. The combination of infrared coupling system and homing optical system can constitute an infrared projective optical system with a magnification of 4.5. The IRCRT image can be projected on the receiver of homing optical system through an infrared projective optical system. SiGeSi is selected as optical material based on the design characteristics and technical specification of infrared coupling system, and the design of the optical system with a Cooke threelens structure has been implemented. The design and assessment results indicate that the optical performance and image quality of the system can meet the design specification.